All FW organismsmaintain internal salt concentrations above
those of the surrounding environment and fall in the category of
osmoregulators. They also all must regulate internal acid–base
balance and excrete nitrogenous waste. The commonality of all
FW organisms relying on active uptake of Na+ combined withthe specific action of Cu on Na+ uptake pathways (Grosell et al.,
2002;Grosell andWood, 2002) explainwhy the FWBLMis successful in predicting acute toxicity in both fish and invertebrates.
However, it should be noted that although the BLMaccounts formuch of the variation in Cu toxicity associatedwithwater chemistry, considerable variation in sensitivity exists among species.
An examination of available data for Cu sensitivity in FWorganisms revealed that the majority of this among-species variation
could be accounted for by differences in size or rather differences in rates of Na+ turnover (Grosell et al., 2002). A strong
correlation exists between Na+ turnover rates and size in FW
organisms (Grosell et al., 2002). Currently the strong influence
of size is not recognized by the BLM and species differences
in sensitivity are simply dealt with through adjustments of constants characterizing the metal/gill interaction. In this regard,
it should be realized that reported acute Cu toxicity values (asLC50’s) span three orders of magnitude.Water chemistry alone
certainly can influence acute toxicity to a single species by as
much as one order ofmagnitude but this leaves themajority of the
overall variation unaccounted for. A large portion of the remaining variation is due to differences in size and thus difference in
physiology among tested species (Grosell et al., 2002).
All FW organismsmaintain internal salt concentrations abovethose of the surrounding environment and fall in the category ofosmoregulators. They also all must regulate internal acid–basebalance and excrete nitrogenous waste. The commonality of allFW organisms relying on active uptake of Na+ combined withthe specific action of Cu on Na+ uptake pathways (Grosell et al.,2002;Grosell andWood, 2002) explainwhy the FWBLMis successful in predicting acute toxicity in both fish and invertebrates.However, it should be noted that although the BLMaccounts formuch of the variation in Cu toxicity associatedwithwater chemistry, considerable variation in sensitivity exists among species.An examination of available data for Cu sensitivity in FWorganisms revealed that the majority of this among-species variationcould be accounted for by differences in size or rather differences in rates of Na+ turnover (Grosell et al., 2002). A strongcorrelation exists between Na+ turnover rates and size in FWorganisms (Grosell et al., 2002). Currently the strong influenceof size is not recognized by the BLM and species differencesin sensitivity are simply dealt with through adjustments of constants characterizing the metal/gill interaction. In this regard,it should be realized that reported acute Cu toxicity values (asLC50’s) span three orders of magnitude.Water chemistry alonecertainly can influence acute toxicity to a single species by asmuch as one order ofmagnitude but this leaves themajority of the
overall variation unaccounted for. A large portion of the remaining variation is due to differences in size and thus difference in
physiology among tested species (Grosell et al., 2002).
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